During heart surgery, the lungs of a patient may be deflated and the heart may be temporarily stopped in order to increase a surgeon's access to the heart and reduce an amount of blood within the surgical field. Often, the heart of the patient is coupled to a cardiopulmonary bypass (CPB) machine, also referred to as a heart-lung machine (HLM), to enable extracorporeal circulation (ECC) of the blood of the patient. The blood is routed from the body of the patient through an ECC circuit of the heart-lung machine. The CPB machine provides oxygen to the blood and circulates the blood through the patient's body.
To maintain anesthesia of the patient during the surgery, volatile anesthetic agents may be administered to the blood of the patient via an anesthetic vaporizer mounted on the heart-lung machine. The anesthetic vaporizer is often positioned between a fresh gas mixer and a membrane oxygenator of the ECC circuit. Carrier gas (most typically a mixture of oxygen and fresh air) from the fresh gas mixer flows into the vaporizer and blends (e.g., mixes and converges) with the anesthetic agent vapors generated by the vaporizer. The amount of carrier gas flowing into the vaporizer may be adjusted by an operator of the vaporizer (e.g., a perfusionist) in order to adjust a ratio of carrier gas to anesthetic agents within the vaporizer. The mixed gases then flow to an inlet of the membrane oxygenator of the CPB machine in order to provide gas exchange between the blood of the patient and the mixed gases from the vaporizer. The anesthetic agents are absorbed by the blood, providing anesthesia to the patient as the blood is returned to the body.